The present invention relates to a signal transfer system which prevents charges which do not change with time from being injected as signal charges in order to prevent saturation of transfer charges and which is particularly suitable to a tapped, charge coupled device (CCD).
As is well known, a CCD has a semiconductor substrate and electrodes insulated from the substrate and serially transfers signal charges of minority carriers stored in potential wells formed in the semiconductor substrate beneath the electrodes, in a longitudinal direction of a channel by applying a multiphase voltage to the electrodes. It has many applications in the field of signal processing such as a delay line for an analog signal.
Two methods for injecting signal charges to the CCD, are the diode cutoff method and the potential balance method which are disclosed in a Japanese version of "Charge Transfer Devices" by C. H. Sequin and M. F. Tompsett, in Bell Telephone Lab. in U.S.A., published Feb. 20, 1978, pages 42-46. However, neither of those methods teaches an efficient way to transfer charges nor suppression of transfer of spurious charges other than signal charges.